Modified lignin reinforced rubber and preparation method therefor

Abstract

Disclosed are a modified lignin reinforced rubber and a preparation method therefor. The modified lignin is obtained by subjecting a compound containing a carbon-carbon double bond, a compound containing a sulfur element and a compound capable of blocking a hydroxyl group to composite modification. In the present invention, lignin is modified with the compound containing a carbon-carbon double bond, and the contained double bond and an olefin in a rubber generate a bonding effect, and the binding force between the lignin and the rubber is improved. Further, by means of modifying the lignin with the compound containing a sulfur element, the lignin contains a certain amount of the element sulfur, the acting force between the lignin and the rubber is improved, the performance of the rubber is improved, the use of a vulcanizing agent can be reduced, and the replacement amount of the lignin to carbon black is further increased. In addition, in the present invention, after being modified by the compound capable of blocking a hydroxyl group, the polarity of the lignin can be significantly reduced, such that the polarity of the lignin is closer to that of the rubber, the acting force between the rubber and the lignin is further improved, and the performance of the rubber is improved.

Description

A modified lignin-reinforced rubber and its preparation method Technical Field

[0001] This invention belongs to the field of rubber, specifically relating to a modified lignin-reinforced rubber and its preparation method. Background Technology

[0002] Natural rubber (NR) is a natural polymer compound with cis-1,4-polyisoprene as its main component. 91%–94% of its composition is rubber hydrocarbon (cis-1,4-polyisoprene), with the remainder consisting of non-rubber substances such as proteins, fatty acids, ash, and sugars. Natural rubber is the most widely used general-purpose rubber. Currently, to further improve rubber performance while reducing costs in the rubber industry, it is usually necessary to fill the rubber compound with other materials. [1] Examples of suitable materials include carbon black and silica. In recent years, research on the application of inorganic materials such as clay, calcium carbonate, talc, and montmorillonite in rubber has also increased. However, with increasing energy scarcity, there is an urgent need to find new energy sources for sustainable development.

[0003] Lignin, as the world's second largest biomass resource after cellulose, possesses a highly cross-linked molecular structure and excellent properties such as anti-aging and thermal stability. Its application in the rubber industry is showing a gradual upward trend. This effectively solves the problem of environmental pollution caused by its long-standing use as waste in the biorefining and papermaking industries, while also enabling the renewable utilization of the resource. (Zhang Cuimei) [2] Researchers have studied the direct application of alkali lignin to rubber. The results showed that when alkali lignin was added at 10%–50%, the compound contained almost no filler network, and the rubber-filler interaction was weak, leading to agglomeration of alkali lignin particles. Therefore, when lignin is directly applied to rubber, agglomeration occurs, which is detrimental to improving additive properties. Our previous research, "A Lignin-Unsaturated Carboxylate Composite Reinforcing Agent and Its Application in Rubber," showed that utilizing the chelating effect between the polar groups of lignin and the metal ions of unsaturated carboxylate can effectively weaken the intermolecular forces of lignin, thereby reducing agglomeration and promoting lignin dispersion in the rubber matrix. Furthermore, it facilitates ionic cross-linking during rubber vulcanization, thus improving the mechanical properties of the rubber. However, this method involves grinding lignin and unsaturated carboxylate to obtain the lignin-unsaturated carboxylate, which is energy-intensive, generates dust pollution, and leads to uneven particle size, thus affecting the rubber's performance. Meanwhile, this modification method does not significantly alter the interaction between lignin and rubber. Therefore, there is a need to develop a new, convenient, low-energy-consumption, and environmentally friendly modification method to promote the application of lignin in the rubber industry.

[0004] [1] Koyama Tanetoshi, A. Steinbeckel. Biopolymers (Volume 2), Polyisoprene [M]. Beijing: Chemical Industry Press, 2004.

[0005] [2] Zhang Cuimei, Cui Xuejing, Sun Yanni, Jiang Ruiyu, Zhao Jiruo, Feng Ying. Study on the properties of alkali lignin-filled natural rubber [J]. Biomass Chemical Engineering, 2017 / No.3.

[0006] Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a modified lignin-reinforced rubber that addresses the shortcomings of the prior art.

[0008] Invention Concept: In the prior art, the uneven dispersion of lignin and the relatively weak bonding strength between lignin and rubber have limited its development in the rubber industry. Therefore, this invention addresses these problems by developing a method to modify lignin using compounds containing carbon-carbon double bonds, compounds containing sulfur, and compounds capable of blocking hydroxyl groups, before applying it to the rubber industry. Firstly, lignin is modified with compounds containing carbon-carbon double bonds and compounds containing sulfur, enabling the lignin to have long chains with carbon-carbon double bonds and a certain amount of sulfur. When reacting with rubber, the double bonds can bond with the olefins in the rubber, increasing the bonding force between lignin and rubber. Furthermore, the modified lignin chains can also entangle with the rubber, further enhancing the interaction force. Additionally, the sulfur content in the modified lignin further improves the bonding force with rubber during vulcanization, resulting in improved rubber performance and reduced vulcanizing agent usage. Finally, modification with compounds that block hydroxyl groups significantly reduces the polarity of lignin, making the polarity of lignin and rubber more similar, thereby further enhancing the interaction force between rubber and lignin and improving the overall performance of the rubber.

[0009] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned modified lignin-reinforced rubber.

[0010] To address the aforementioned technical problems, this invention discloses a method for preparing modified lignin-reinforced rubber; wherein the modified lignin is prepared by composite modification of lignin with compounds containing carbon-carbon double bonds, compounds containing sulfur elements, and compounds capable of blocking hydroxyl groups.

[0011] If the compound can contain both carbon-carbon double bonds and sulfur, then only this compound can be used to replace compounds containing only carbon-carbon double bonds and compounds containing only sulfur.

[0012] The lignin mentioned therein is any one or a combination of several of alkali lignin, soda lignin, organic solvent lignin, and enzymatically hydrolyzed lignin.

[0013] The compound containing carbon-carbon double bonds is a compound containing any one of the following groups: vinyl, acrylic, butadiene, oleic, linoleic, linolenic, arachidonic, and phthalic acid diene.

[0014] Preferably, the compound containing carbon-carbon double bonds is a compound containing any one or a combination of vinyl and acrylic groups.

[0015] The acrylic acid-containing compounds include, but are not limited to, zinc acrylate, magnesium acrylate, and calcium acrylate.

[0016] More preferably, the compound containing carbon-carbon double bonds is a long-chain compound containing no less than five carbon atoms; more preferably, it is a long-chain compound containing no less than ten carbon atoms.

[0017] More preferably, the long-chain modifier is a vinylsilane; wherein the vinylsilane is any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinyl(2-methoxyethoxy)silane, and vinyltriacetoxysilane.

[0018] The sulfur-containing compound is any one or a combination of several of the following: mercaptosilane coupling agent of Formula I, bis-[γ-(triethoxysilane)propyl]tetrasulfide, thiol, potassium persulfate, mercaptobenzothiazole, sulfur, and tetramethylthiuram monosulfide; preferably, the sulfur-containing compound is any one or a combination of several of the following: bis-[γ-(triethoxysilane)propyl]tetrasulfide, mercaptobenzothiazole, sulfur, and tetramethylthiuram monosulfide.

[0019]

[0020] In the formula, R1, R2, and R3 are each independently selected from -O-R6; wherein R6 is selected from alkyl, alkenyl, aryl, or aralkyl; and R4 is selected from -(CH2). n -; where n is selected from any integer from 1 to 10; R5 is selected from H, CN, or (C=O)-R. 6 Among them, R 6 Selected from branched or unbranched, saturated or unsaturated aliphatic, aromatic or mixed aliphatic / aromatic hydrocarbon groups with a single C1-C30 hydrocarbon group.

[0021] Preferably, R1, R2, and R3 are each independently selected from -OCH3 or -OCH2CH3; n is selected from 2 to 10; and R5 is H.

[0022] Further preferably, the mercaptosilane coupling agent shown in Formula I is 3-mercaptopropyltriethoxysilane or (3-mercaptopropyl)trimethoxysilane.

[0023] The compound capable of blocking hydroxyl groups is any one or a combination of several of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0024] The silane coupling agent includes, but is not limited to, vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinyl(2-methoxyethoxy)silane, vinyltriacetoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimeth(eth)oxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane; more preferably, the silane coupling agent is any one or a combination of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinyl(2-methoxyethoxy)silane, and vinyltriacetoxysilane.

[0025] The titanate coupling agents include, but are not limited to, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl dioleoyl oxy(dioctyl pyrophosphate) titanate, monoalkoxy unsaturated fatty acid titanate, chelates of bis(dioctyl pyrophosphate) ethylene titanate and triethanolamine, and bis(dioctyl pyrophosphate) ethylene titanate.

[0026] The modified lignin is prepared by any one of the following methods:

[0027] (1) Impregnation method: Lignin and modifier are impregnated in ethanol, methanol, acetone or water, and then dried to obtain the product;

[0028] (2) Blending method: lignin and modifier are blended together in a mixer to obtain the desired product;

[0029] (3) Airflow modification method: The modifier is prepared into a methanol, ethanol or acetone solution (if the modifier is a liquid, it does not need to be prepared into a solution, it can be sprayed directly), and then the lignin is modified by an integrated airflow pulverization and surface modification machine; wherein, the integrated airflow pulverization and surface modification machine has been disclosed in CN101433876B Integrated airflow pulverization and surface modification device and its process for preparing ultrafine particles.

[0030] Preferably, the above-mentioned method for preparing modified lignin involves first modifying it by adding compounds containing carbon-carbon double bonds and compounds containing sulfur elements, and then modifying it by adding compounds that can block hydroxyl groups.

[0031] The impregnation method preferably includes the following steps:

[0032] (I) A first solution is obtained by dispersing a compound containing a carbon-carbon double bond and a compound containing a sulfur element in ethanol; a second solution is obtained by dispersing a compound that can block hydroxyl groups in ethanol.

[0033] (II) Disperse lignin in the first solution until the lignin reaches the impregnation state (if the impregnation state cannot be achieved after adding the ethanol solution of the modifier, ethanol can be added directly to make the lignin reach the impregnation state), to obtain an ethanol solution of lignin, let it stand and dry.

[0034] (III) Disperse the lignin obtained in step (II) in the second solution until the lignin reaches the impregnation state (if the impregnation state cannot be achieved after adding the ethanol solution of the modifier, ethanol can be added directly to make the lignin reach the impregnation state), and obtain the ethanol solution of lignin. Let it stand and dry to obtain the final product.

[0035] In step (I), the dispersion is achieved by adding ethanol dropwise to compounds containing carbon-carbon double bonds and compounds containing sulfur.

[0036] In step (I), there are no specific requirements for the concentration of compounds containing carbon-carbon double bonds, compounds containing sulfur elements, and compounds that can block hydroxyl groups; they only need to be evenly dispersed, and are preferably 1 to 8 g / mL.

[0037] In step (II), the dispersion is achieved by adding the first solution dropwise to the lignin; the amount of the compound containing carbon-carbon double bonds and the compound containing sulfur elements are both 1 to 4 wt% of the lignin, preferably 2 wt%.

[0038] In step (III), the dispersion is a second solution added dropwise to the lignin obtained in step (II); the amount of the compound that can block hydroxyl groups is 0.5 to 4 wt% of the lignin.

[0039] There are no specific requirements for the dripping rate in the above process.

[0040] The preferred method of blending involves placing lignin, a compound containing carbon-carbon double bonds, and a compound containing sulfur elements in a mixer and blending them until the mixer temperature reaches 90–120°C. Then, a compound capable of blocking hydroxyl groups is added and blended for 10–20 minutes. The amounts of the compound containing carbon-carbon double bonds and the compound containing sulfur elements are both 1–4 wt% of the lignin; the amount of the compound capable of blocking hydroxyl groups is 0.5–0.8 wt% of the lignin.

[0041] The airflow modification method preferably includes the following steps:

[0042] (i) Disperse compounds containing carbon-carbon double bonds and compounds containing sulfur elements in ethanol to obtain a third solution; disperse compounds that can block hydroxyl groups in ethanol to obtain a fourth solution;

[0043] (ii) The third solution is sprayed into the pulverizing chamber through an atomizing nozzle, so that the compounds containing carbon-carbon double bonds and the compounds containing sulfur elements are adsorbed onto the lignin surface in the pulverizing chamber and pulverized for 2 to 3 minutes.

[0044] (iii) The fourth solution is sprayed into the pulverizing chamber through an atomizing nozzle, so that the compound that can block hydroxyl groups is adsorbed on the lignin surface in the pulverizing chamber and pulverized for 2 to 4 minutes; then separated by a cyclone separator to obtain the final product.

[0045] In step (i), there are no specific requirements for the concentration of compounds containing carbon-carbon double bonds, compounds containing sulfur elements, and compounds that can block hydroxyl groups; they only need to be evenly dispersed, and are preferably 1 to 8 g / mL.

[0046] In step (ii), the amount of compounds containing carbon-carbon double bonds and compounds containing sulfur elements is 1 to 4 wt% of lignin; the temperature of the pulverizing air is 90 to 120°C.

[0047] In step (iii), the amount of the compound that can block hydroxyl groups is 0.5 to 0.8 wt% of lignin; the temperature of the pulverizing air is 90 to 120°C.

[0048] The rubber mentioned herein is any one of natural rubber, butyl rubber, and styrene-butadiene rubber.

[0049] The preparation method of the modified lignin-reinforced rubber includes the following steps:

[0050] (1) Modified lignin, rubber, carbon black, vulcanizing agent and vulcanizing aid are added to a mixer and mixed to obtain a compound rubber;

[0051] (2) After repeatedly passing the compound obtained in step (1) through a two-roll mill, its vulcanization performance is measured by a rubber vulcanizer and hot-pressed into shape by a flat vulcanizer.

[0052] In step (1), the mass ratio of modified lignin to rubber is (2-50):100.

[0053] In step (1), the mass ratio of rubber, carbon black, vulcanizing agent and vulcanizing auxiliaries is 100:(1~20):(0.5~2.5):(0.5~10); the mixing temperature is 20~120℃ and the mixing time is 5~30min.

[0054] In step (2), the number of thin passes is 5 to 30; the temperature of the flat vulcanizing machine is 120 to 180°C, and the hot pressing time is the positive vulcanization time t measured by the rubber vulcanizing instrument. 90 .

[0055] The modified lignin-reinforced rubber prepared by the above method is also within the scope of protection of this invention.

[0056] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0057] (1) The present invention modifies lignin with a compound containing carbon-carbon double bonds, so that the lignin can have a long chain containing carbon-carbon double bonds, so that when it interacts with rubber, the double bonds can form a bonding reaction with the olefins in the rubber, thereby improving the bonding force between lignin and rubber. Furthermore, the modified lignin long chain can also entangle with the rubber, further improving the interaction force between the two.

[0058] (2) The present invention modifies lignin by using a compound containing sulfur, so that the lignin contains a certain amount of sulfur. Sulfur can improve the interaction between lignin and rubber, thereby further improving the performance of the prepared rubber, reducing the use of vulcanizing agent, and further increasing the amount of carbon black replaced by lignin.

[0059] (3) The present invention modifies lignin by using compounds that can block hydroxyl groups, which significantly reduces the polarity of lignin, making the polarity of lignin and rubber closer, thereby further improving the interaction between rubber and lignin and improving the overall performance of rubber; at the same time, after hydroxyl blocking, there is less lignin aggregation, thereby further improving the dispersibility of lignin in rubber.

[0060] (4) Compared with one-pot modification, the present invention first modifies lignin with compounds containing carbon-carbon double bonds and compounds containing sulfur elements, and then modifies it with compounds that can block hydroxyl groups, which can effectively improve the modification effect of lignin. Attached Figure Description

[0061] Figure 1 shows the water contact angles of lignin modified with different coupling agents.

[0062] Figure 2 shows the properties of the rubber in Example 4. Detailed Implementation

[0063] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0064] The detection method in this embodiment is as follows:

[0065] Water contact angle test: The pre-dried lignin sample was pressed into a uniform thin sheet using an infrared tablet press, and the water contact angle of the sample sheet was measured using a contact angle tester.

[0066] Particle size test: The dried lignin sample was added to water at a solid-liquid ratio of 1:50, ultrasonically dispersed for 30 min, and an appropriate amount was dropped into a laser particle size analyzer for particle size analysis.

[0067] The tensile properties of the rubber were tested on a UTM6104 electronic universal testing machine according to GB / T528-2009.

[0068] The method for testing the hardness of rubber involves placing the sample on a Shore hardness tester A, pressing down the handle to make the indenter of the hardness tester make horizontal contact with the sample, and taking the reading within 1 second.

[0069] Example 1: Preparation of modified lignin (impregnation method)

[0070] According to Table 1, weigh out the compounds containing carbon-carbon double bonds and the compounds containing sulfur, stir and mix them well, then add ethanol to them. The concentration of the compounds containing carbon-carbon double bonds and the compounds containing sulfur is 2 g / mL, to obtain the first solution. According to Table 1, weigh out the compounds that can block hydroxyl groups, add ethanol to them, and the concentration of this substance is 2 g / mL, to obtain the second solution. If the compounds containing carbon-carbon double bonds, the compounds containing sulfur, and the compounds that can block hydroxyl groups in Table 1 do not need to be dissolved in ethanol, they can be used directly. Control the amount of these compounds according to the description in the following two paragraphs.

[0071] The first solution was added dropwise to 10g of enzymatically hydrolyzed lignin (the amount of compounds containing carbon-carbon double bonds and compounds containing sulfur elements were both 2wt% of the amount of enzymatically hydrolyzed lignin), and then ethanol (about 8mL) was added dropwise until the lignin was impregnated. The mixture was thoroughly mixed and allowed to stand for 30min. The modified lignin was then placed in a vacuum drying oven and vacuum dried at 60℃ to allow the ethanol to evaporate completely. Finally, it was pulverized for 2min using a pulverizer.

[0072] The second solution was added dropwise to the pulverized material (the compound that can block hydroxyl groups was used as 4% of the enzymatic hydrolysis system), and then ethanol was added dropwise until the lignin was impregnated. The mixture was thoroughly mixed and allowed to stand for 30 minutes. The modified lignin was then placed in a vacuum drying oven and dried at 60°C to allow the ethanol to evaporate completely. Finally, it was pulverized for 1 minute using a pulverizer.

[0073] Table 1

[0074]

[0075]

[0076] Analyze the results based on Table 2 and Figure 1:

[0077] (1) The contact angle of the modified enzymatic hydrolyzed lignin was tested. As can be seen from Table 2, the contact angle of the modified lignin was improved compared to the contact angle of the unmodified enzymatic hydrolyzed lignin, which was 62°.

[0078] (2) Compared to other modifications, Examples 1-12 did not block the hydroxyl groups, and the contact angle of the modified lignin was 80°, which was lower than that of the other examples in Example 1. This shows that it is very necessary to use a substance that can block the hydroxyl groups for modification. Examples 1-1 to 1-3 used different compounds to block the hydroxyl groups of enzymatically hydrolyzed lignin, and the contact angles of the three were relatively similar.

[0079] (3) Examples 1-4 to 1-8 studied the effect of different sulfides on the contact angle. The results showed that, except for Examples 1-7 and 1-8, different sulfides did not have a significant effect on the contact angle. This is because Examples 1-7 and 1-8 used silane coupling agents, which contain thiol groups and silanes, and have a certain blocking effect on hydroxyl groups.

[0080] (4) Examples 1-9 to 1-11 used different compounds containing carbon-carbon double bonds for modification, and the hydroxyl groups were blocked with vinyltriacetoxysilane. Compared with acrylic acid, these three examples used long chains containing double bonds for modification. The contact angle of the modified lignin was significantly improved. In particular, the contact angle of Example 1-9 reached 101°, indicating that the polarity of lignin was greatly improved.

[0081] Table 2

[0082]

[0083] Example 2: Preparation of modified lignin (airflow modification method)

[0084] Prepare the first and second solutions according to numbers 4, 9, 10, and 12 in Table 1, following the same method as in Example 1.

[0085] Enzymatically hydrolyzed lignin was injected into a grinding chamber using high-pressure air at approximately 100°C. Simultaneously, a first solution (flow rate of 40 mL / min) was sprayed into the grinding chamber through an atomizing nozzle. The air classifier rotated at 2000 rpm for 2 minutes. Then, a second solution (flow rate of 40 mL / min) was sprayed into the grinding chamber through an atomizing nozzle, and the air classifier rotated at 2000 rpm for 3 minutes. After separation by a cyclone separator, four modified lignins were obtained: lignin4, lignin9, lignin10, and lignin12. The particle size was measured using a Macchiato S3500 laser particle size analyzer. The D50 values ​​for the three were 1.6 μm, 1.4 μm, 1.7 μm, and 2.3 μm, respectively. In Example 1, the modified lignin prepared using the same method had a larger particle size. This demonstrates that air jet milling can further reduce the particle size of lignin, thus making it more suitable for applications in rubber.

[0086] Example 3: Preparation of lignin-reinforced rubber

[0087] (1) Take 10g of enzymatically hydrolyzed lignin (particle size pulverized to 2.1μm by airflow) and lignin4, lignin9, lignin10, lignin12 prepared in Example 2, and lignin13, lignin14 (numbers 13 and 14 in Table 1) prepared in Example 2, and add them to a mixer in sequence with 40g of natural rubber, 10g of high abrasion-resistant carbon black N330, 1g of sulfur, 0.6g of N-cyclohexyl-2-benzothiazole sulfenamide, 2g of zinc oxide and 0.8g of stearic acid, and mix them at 100°C for 20min.

[0088] (2) Place the rubber compound obtained in step (1) into a two-roll mill and pass it through a thin mill 7 times to produce sheets. Measure its vulcanization performance using a rubber vulcanizing apparatus to obtain the positive vulcanization time t at 180℃. 90 The curing time was 3 minutes. The rubber was hot-pressed at 180℃ for 3 minutes using a flat vulcanizing machine. The resulting rubbers were named Ru-lignin, Ru-lignin4, Ru-lignin9, Ru-lignin10, Ru-lignin12, Ru-lignin13, and Ru-lignin14, respectively. The test results are shown in Table 3.

[0089] Table 3 Properties of vulcanized rubber

[0090]

[0091] As shown in Table 3, under the same particle size, the performance of rubber prepared from modified lignin is significantly improved compared to unmodified lignin. Specifically, compared to unblocked lignin lignin 12, lignin 13, and lignin 14, lignin 4, lignin 9, and lignin 10, modified with all three compounds simultaneously, show a significant improvement in rubber performance after increasing the contact angle. Furthermore, lignin 4 is modified with zinc acrylate for double bond modification. Although the chain length of zinc acrylate is not as long as that of vinyltrimethoxysilane, zinc acrylate facilitates vulcanization with rubber, thus achieving a similar effect to lignin 9.

[0092] Example 4

[0093] The preparation method of Ru-lignin9 in Example 3 was the same, except that natural rubber was replaced with butyl rubber and chloroprene rubber. The properties of the butyl rubber preparation were tested, and its tensile strength, elongation at break, stress at 300% elongation, stress at 100% elongation, tensile permanent deformation, and hardness were 27.8 MPa, 870%, 7.5 MPa, 3.6 MPa, 11.7%, and 79%, respectively. The properties of the chloroprene rubber preparation were tested, and its tensile strength, elongation at break, stress at 300% elongation, stress at 100% elongation, tensile permanent deformation, and hardness were 18.3 MPa, 578%, 5.8 MPa, 4.4 MPa, 3.9%, and 65%, respectively. Therefore, compared to natural rubber, the modified lignin prepared in this invention is not suitable for polar chloroprene rubber.

[0094] Comparative Example 1: Preparation methods with other sequences

[0095] Modified lignin was prepared according to the formula number 9 in Table 1, using the same preparation method as in Example 2, except that the order of the first solution and the second solution was reversed, resulting in modified lignin lignin91.

[0096] Modified lignin was prepared according to the formula number 9 in Table 1, using the same preparation method as in Example 2, except that the first and second solutions were mixed. Specifically, the enzymatically hydrolyzed lignin was injected into the grinding chamber using high-pressure air at approximately 100°C. Simultaneously, the mixture of the first and second solutions (flow rate of 40 mL / min) was sprayed into the grinding chamber through an atomizing nozzle. The airflow classifier rotated at 2000 rpm for 5 minutes, and then the mixture was separated by a cyclone separator to obtain modified lignin lignin92.

[0097] Similar to the preparation method of Ru-lignin9 in Example 3, lignin9 was replaced with lignin91 and lignin92 respectively to prepare rubbers Ru-lignin91 and Ru-lignin92. Performance testing of the rubbers, as shown in Table 4, revealed that compared to the preparation sequence of this invention, changing the order of the first and second solutions (i.e., first sealing the hydroxyl groups, then using compounds containing sulfur and compounds containing double bonds for modification) resulted in worse performance than using all three solutions together.

[0098] Table 4

[0099]

[0100]

[0101] Comparative Example 4:

[0102] Modified lignin was prepared according to the formulation in Table 1, No. 9, using the same preparation method as in Example 2. The three compounds were prepared into solutions. The enzymatically hydrolyzed lignin was then injected into the pulverizing chamber using high-pressure air at approximately 100°C. The solutions of the three compounds (flow rate 40 mL / min) were then sprayed into the pulverizing chamber through atomizing nozzles. The airflow classifier rotated at 2000 rpm for 5 minutes. After separation by a cyclone separator, the modified lignins lignin93 (vinyltrimethoxysilane modified), lignin94 (2-mercaptobenzothiazole modified), and lignin95 (vinyltriacetoxysilane) were obtained.

[0103] Using the same preparation method as Ru-lignin9 in Example 3, lignin9 was replaced with lignin93, lignin94, and lignin95 respectively to prepare rubbers Ru-lignin93, Ru-lignin94, and Ru-lignin95. The performance of the rubbers was tested, and the results are shown in Table 5. As can be seen from Table 5, although there is some improvement in performance, the improvement effect is small. Only when all three are used simultaneously does the present invention achieve a better effect.

[0104] Table 5

[0105]

[0106] Example 5:

[0107] The preparation method for Ru-lignin9 in Example 3 was the same, except that the amount of lignin9 was replaced with 20 parts, 30 parts, 40 parts, and 50 parts, respectively. The resulting rubbers were designated as Ru-lignin9-20, Ru-lignin9-30, Ru-lignin9-40, and Ru-lignin9-50, respectively. Similarly, the preparation method for Ru-lignin12 in Example 3 was the same, except that the amount of lignin12 was replaced with 20 parts, 30 parts, 40 parts, and 50 parts, respectively. The resulting rubbers were designated as Ru-lignin12-20, Ru-lignin12-30, Ru-lignin12-40, and Ru-lignin12-50, respectively. The test results are shown in Figure 2. As can be seen from the figure, the amount of lignin9 can reach 50 parts. Although its performance decreases at 50 parts, it is still higher than the original amount of 10 parts. As for Ru-lignin12, its performance decreases at 30 parts with the increase of lignin12 amount. Therefore, the long-chain modifier containing double bonds selected in this invention can significantly improve the performance of rubber after modifying lignin, and also further increase its substitution for carbon black.

[0108] This invention provides a modified lignin-reinforced rubber and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing modified lignin-reinforced rubber, It is characterized in that The modified lignin is prepared by compositely modifying lignin with a compound containing a carbon-carbon double bond, a compound containing sulfur elements and a compound capable of sealing a hydroxyl group.

2. The method for preparing the modified lignin-reinforced rubber according to claim 1, It is characterized in that The lignin is any one or a combination of alkali lignin, soda lignin, organic solvent lignin and enzymatic lignin.

3. The method for preparing the modified lignin-reinforced rubber according to claim 1, It is characterized in that The compound containing a carbon-carbon double bond is a compound containing any one of vinyl, acrylic, butadienyl, oleic, linoleic, linolenic, arachidonic and phthalic acid diene groups.

4. The method for preparing the modified lignin reinforced rubber according to claim 2 or 3, It is characterized in that The compound containing a carbon-carbon double bond is a long-chain compound containing no less than five carbon atoms.

5. The method for preparing the modified lignin reinforced rubber according to claim 1, It is characterized in that The sulfur-containing compound is any one or a combination of mercaptosilane coupling agent, bis-[γ-(triethoxysilyl)propyl] tetrasulfide, mercaptan, potassium persulfate, mercaptobenzothiazole, sulfur and tetramethylthiuram monosulfide as shown in formula I; In the formula, R 1 , R 2 , R 3 are independently selected from -OR 6 ; Among them, R 6 is selected from alkyl, alkenyl, aryl or aralkyl; The R 4 Selected from -(CH 2 ) n -; wherein n is selected from any integer from 1 to 10; The R 5 Selected from H, CN or (C=O)-R 6 ; Among them, R 6 A monovalent C1-C30 hydrocarbon group selected from branched or unbranched, saturated or unsaturated aliphatic, aromatic or mixed aliphatic / aromatic.

6. The method for preparing the modified lignin reinforced rubber according to claim 1, It is characterized in that The compound capable of sealing hydroxyl groups is any one or a combination of silane coupling agents, titanate coupling agents and aluminate coupling agents.

7. The method for preparing the modified lignin reinforced rubber according to claim 1, It is characterized in that The preparation method of the modified lignin is to first add a compound containing a carbon-carbon double bond and a compound containing a sulfur element for modification, and then add a compound capable of blocking a hydroxyl group for modification.

8. The method for preparing the modified lignin reinforced rubber according to claim 1, It is characterized in that The rubber is any one of natural rubber, butyl rubber and styrene-butadiene rubber.

9. The method for preparing the modified lignin reinforced rubber according to claim 1, It is characterized in that The steps include: (1) adding the modified lignin, rubber, carbon black, a vulcanizing agent, and a vulcanizing aid into an internal mixer for mixing to obtain a mixed rubber; (2) placing the rubber mix obtained in step (1) in an open mill and repeatedly passing it through a thin mill, measuring its vulcanization performance with a rubber vulcanizer, and hot pressing it with a flat vulcanizer.

10. The method for preparing the modified lignin reinforced rubber according to claim 7, It is characterized in that In step (1), the mass ratio of modified lignin to rubber, carbon black, vulcanizing agent and vulcanization aid is (2-50):100:(1-20):(0.5-2.5):(0.5-10).